# If a Variable X Takes Values 0, 1, 2,..., N with Frequencies Nc0, Nc1, Nc2 , ... , Ncn, Then Write Variance X. - Mathematics

If a variable X takes values 0, 1, 2,..., n with frequencies nC0nC1nC2 , ... , nCn, then write variance X.

#### Solution

$x = \frac{\sum^n_{i = 0} x_i f_i}{\sum^n_{i = 0} f_i} = \frac{0 \times ^{n}{}{C}_o + 1 \times^{n}{}{C}_1 + . . . + n \times ^{n}{}{C}_n}{T^{n}{}{C}_o +^{n}{}{C}_1 + . . . +^{n}{}{C}_n}$

$\Rightarrow x = \frac{n \times 2^{n - 1}}{\frac{2^n}{n + 1}}$

$= \frac{n\left( n + 1 \right)}{2}$

$\therefore Var(X) = \sigma^2$

$= \frac{1}{n} \sum^n_{i = 0} \left( x_i - x \right)^2$

$= \frac{1}{n} \left[ \left( 0 + 1 + 2 + . . . . + n \right) - nx \right]^2$

$\Rightarrow \sigma^2 = \frac{1}{n} \left[ \frac{n\left( n + 1 \right)}{2} - \frac{n \times n\left( n + 1 \right)}{2} \right]^2$

$= \frac{1}{n} \left[ \frac{n\left( n + 1 \right)}{2}\left( 1 - n \right) \right]^2$

$= \frac{n^2}{4n} \left( n + 1 \right)^2 \left( n - 1 \right)^2$

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#### APPEARS IN

RD Sharma Class 11 Mathematics Textbook
Chapter 32 Statistics
Q 7 | Page 49